A swimming pool was sufficiently alkaline so that the carbon dioxide absorbed from the air produced a solution in the pool that was 2 × 10^-4 M in carbonate ion.If the pool originally contained 4 × 10^-3 M Mg²⁺,6 × 10^-4 M Ca²⁺,and 8 × 10^-7 M Fe²⁺,then the precipitate that was formed consisted of ________.
(K_sp values are: CaCO₃,4.7 × 10^-9;MgCO₃,4.0 × 10^-5;FeCO₃,2.0 × 10^-11)

Question

Quizplus · Accepted Answer

The question states that the pool is sufficiently alkaline to have a concentration of 2 × 10^-4 M carbonate ion. This concentration is greater than the solubility product for MgCO3 (4.0 × 10^-5) but less than the solubility product for CaCO3 (4.7 × 10^-9) and FeCO3 (2.0 × 10^-11). Therefore, MgCO3 will not precipitate, but both CaCO3 and FeCO3 will precipitate. Thus, the precipitate will consist of CaCO3 and FeCO3, making the correct answer choice D.

A Swimming Pool Was Sufficiently Alkaline So That the Carbon